An orthogonally projected image forming unit 1 forms an orthogonally projected image based on a photographed image. A direction specifying unit 2 enables the orthogonally projected image to be seen from a different viewpoint, and forms an orthogonally projected image seen from a different viewpoint. A feature extracting unit 3 extracts a feature from the orthogonally projected image. A symbol pasting unit 4 pastes a symbol to a drawing during plotting. A display unit 5 displays the formed orthogonally projected image, the orthogonally projected image formed by changing a viewpoint, the orthogonally projected image processed by the image feature extracting unit 3, and the symbol pasted by the symbol pasting unit 4, and so on. An I/O unit 6 inputs/outputs various image data or three-dimensional coordinate data from a three-dimensional coordinate input de-vice such as a survey instrument or the like to the other device. Accordingly, plotting can be performed even for a spot unseen on an orthogonally projected image or a spot that has not been measured by forming the orthogonally projected image seen from the different viewpoint and pasting the symbol.